Data from the second black box found in the wreckage of the Germanwings flight that crashed last week in the French Alps confirm the co-pilot acted deliberately, investigators say.

"A first reading shows that the pilot in the cockpit used the automatic pilot to descend the plane towards an altitude of 100 feet (30 metres)," said the French BEA crash investigation office in a statement on Friday.

"Then, several times during the descent, the pilot changed the automatic pilot settings to increase the aircraft's speed," added the investigators.

The latest information appeared to confirm the theory that co-pilot Andreas Lubitz deliberately smashed his plane into the mountains, killing all 150 people on board.

Authorities found the second black box, which contains technical flight data, on Thursday after a gruelling nine-day search in difficult mountain terrain.

Data from the first black box, which records conversations in the cockpit, suggested that Lubitz, 27, locked his captain out and then deliberately set the plane on a deadly collision course with the mountains.

The plane smashed into the mountains at a speed of 700 kilometres an hour, instantly killing everyone on board - half of them German and more than 50 from Spain.